<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1 {
            width: 300px;
            height: 100px;
            border: 10px solid red;
            /*设置圆角 值越大越圆,超过宽高一半为正圆*/
            border-radius: 100px;
        }
        #d2{
            width: 100px;
            height: 100px;
            border: 1px solid blue;
            /*给元素添加内边距默认情况下会影响宽高*/
            padding-left: 50px;
            padding-top: 50px;
            /*添加下面样式之后,内边距不影响所占宽高*/
            box-sizing: border-box;
        }
        body{margin: 0}
        *{margin: 0;padding: 0}
        p,ul{margin: 0;padding: 0}
    </style>
</head>
<body>
<p>段落1</p>
<p>段落2</p>
<h1>内容标题1</h1>
<h2>内容标题2</h2>
<ul>
    <li>aaa</li>
    <li>bbb</li>
    <li>ccc</li>
</ul>
<input type="text">
<div id="d1">边框测试</div>
<div id="d2">内边距</div>

</body>
</html>